(1) Field of the Invention
The present invention relates to a display device, and in particular, to a liquid crystal lens provided on the display side of a display panel.
(2) Description of the Related Art
In recent years, display devices where a liquid crystal panel having lens effects (hereinafter referred to as liquid crystal lens) is provided on the display side of a liquid crystal display panel or an organic EL display panel so that a two-dimensional display (2-D display) and a three-dimensional display (3-D display) can be switched have been known. Such display devices have such a structure that the image for the right eye displayed on the display panel and the image for the left eye are separately viewed by the left and right eyes of the viewer due to the lens effects of the liquid crystal lens.
Such display devices where the 2-D display and the 3-D display can be switched include, for example, three-dimensional display devices as in JP 2010-224191A. The three-dimensional display device in JP 2010-224191A has in its structure a display panel for displaying an image, a birefringent lens provided on the display side of the display panel, and a liquid crystal lens provided between the display panel and the birefringent lens. In the liquid crystal lens, two electrodes in comb form are provided on each of the pair of transparent substrates that are provided so as to face each other with a liquid crystal layer in between. Furthermore, the two electrodes in comb form are formed on each transparent substrate so as to provide such a structure that the two electrodes in comb form alternate within the display region.
The liquid crystal lens in JP 2010-224191A particularly has such a structure that different voltages or the same voltage is applied to the two electrodes in comb form, and this structure makes it possible to switch the display between a 2-D display and a 3-D display and to switch the parallax numbers at the time of 3-D display by controlling the voltage applied to each electrode in comb form. That is to say, in the three-dimensional display device in JP 2010-224191A, a refractive index distributing type (GRIN: gradient index) lens having teeth of odd numbers of the electrode in comb form as end portions is formed in the case where a first voltage is applied to the teeth of the even numbers of the electrode in comb form and the electrode on the transparent substrate that is provided so as to face the electrode in comb form with a liquid crystal layer in between, and at the same time, a second voltage is applied to the teeth of the odd numbers of the electrode in comb form. In addition, a GRIN lens having each tooth of the electrodes in comb form as an end portion is formed in the case where a first voltage is applied to the teeth of even numbers of the electrode in comb form and the teeth of odd numbers of the electrode in comb form, and at the same time, a second voltage is applied to the electrode on the transparent substrate that is provided so as to face this electrode in comb form with a liquid crystal layer in between.
“Autostereoscopic Partial 2-D/3-D Switchable Display Using Liquid-Crystal Gradient Index Lens” (Ayako Takagi et al., SID Digest, 30.3, 2010) also describes a display device where a 2-D display and a 3-D display can be switched. The display device in “Autostereoscopic Partial 2-D/3-D Switchable Display Using Liquid-Crystal Gradient Index Lens” (Ayako Takagi et al., SID Digest, 30.3, 2010) has such a structure that only a liquid crystal lens having lens effects is provided on the display side of the display panel. Here, in the liquid crystal lens, an electrode in comb form is formed on one of the transparent substrates that are provided so as to face each other with a liquid crystal layer in between, and an electrode in plate form is formed on the other transparent substrate. In the liquid crystal lens having this structure, a first voltage is applied to the electrode in comb form, and at the same time, a second voltage is applied to the electrode in plate form so that a GRIN lens is formed having the electrode in comb form as an end portion. “Autostereoscopic Partial 2-D/3-D Switchable Display Using Liquid-Crystal Gradient Index Lens” (Ayako Takagi et al., SID Digest, 30.3, 2010) also describes a liquid crystal lens where two electrodes in comb form are formed on one transparent substrate so as to mesh with each other, and an electrode in plate form is formed on the other transparent substrate as in JP 2010-224191A.